How Flexible Printed Circuits Can Be Produced in High Volume
Flexible Printed Circuits Can Be Produced in High Volume
When designing electronic products it is important to take into consideration all of the forces and stresses that will be placed on the circuit board. These include environmental conditions such as heat, moisture and chemicals; physical stress from bending, pulling or twisting; and shock and vibration. Flexible printed circuits, or flex PCBs as they are more commonly called, can be used to provide a solution to these challenges by helping to improve the overall product reliability and performance.
In addition, a flex circuit can be used to reduce the number of connections between electronic components. This can help to reduce assembly time and costs, as well as improving the overall design flexibility of a product.
Most flex circuits are produced using one of two base materials; polyimide or polyester. Polyimide is the most common, and is a non-flammable, geometrically stable material that is highly resistant to solder reflow temperatures. It is also very tough and can withstand repeated bending and stretching. It is also able to withstand high temperatures, which is essential for most flex circuits.
The conductor layer in a flex circuit is typically copper, and can be either bare or plated. Unplated copper is prone to work hardening and fatigue, making it unsuitable for a flex circuit that will be subjected to repetitive movement or creasing. Rolled annealed (RA) copper is much more springy in the z-direction, and can handle a greater amount of deformation before fatigue cracking starts to occur. It is therefore a very good choice for dynamic flex circuit applications.
How Flexible Printed Circuits Can Be Produced in High Volume
Other layers may be present in a flex circuit, including dielectric, solder mask and coverlay. The dielectric and solder mask layers protect the underlying conductors from corrosion and damage, and prevents solder from connecting to circuit traces. Coverlay is usually screen-printed, and can be any of a range of materials, including PI or PET, and flexible solder mask ink.
A printed flexible circuits may also incorporate rigid components, such as aluminum or stainless steel. These can provide dimensional stability, physical support and stress relief, and can be attached to the flex circuit with adhesive. Rigid components can be added to any type of flex circuit, but are generally used in more complex designs.
Anyone who has ever looked inside a modern mobile phone or laptop computer will have seen the advantages of flexible circuitry. These thin, conductive films and layers can replace many types of traditional wires while providing a more compact, lightweight, reliable and durable solution. Flex PCBs are a major component of today’s mobile consumer electronics and can be found in cameras, calculators, exercise monitors and many other everyday devices.
The success of these revolutionary technologies has been driven largely by their ability to seamlessly integrate form, fit and function, while improving the reliability and performance of the finished products they are used in. To realize these benefits, however, manufacturers need to have a full understanding of the properties of flex and rigid-flex circuits, so they can be designed and produced to ensure their long-term performance.